Railroad Radio

Radio Record, Volume III, Issue 12, 4 October 1929, Page 15

Railroad Radio

aeaoteet et An. Interesting System QwWine to the tremendous lengths of many of the American goodstrains, some means of establishing communication between the engine crew and the guard has had to be devised. The two are frequently over a mile and a half apart, and hence any form of visual communication is obviously impossible, owing to the curves which the train would have to negotiate during its journeys. Telephonic and telegraphic communication has been tried out, but has proved to be unreliable, and mechanical forms of communica~tion are not at all satisfactory. If radio-telephony were to be employed, there were three main difficulties to be overcome, namely, (a) the necessary installatio: had to be constructed to withstand the extreme vibration and joltings of the train, (b) any possible atmospheric interference had to be prevented, and (ec) the installation had of necessity to be foolproof and as simple as possible. However, after many protracted tests, these difficulties were overcome, and an ideal system of shortwave radio-tele-phony communication was devised. The locomotive transmitter, operated by a turbine-driven generator, works on a wavelength of 180 metres (2300 kilocycles), and delivers a power to the aerial of 45 watts. A cone loudspeaker is fitted up in the cab, and produces sufficient volume to override the noises made by the engine. The guard’s equipment at the end of the train is identical with the apparatus employed by the driver. The mode. of operation is such that by depressing a button the equipment transmits, and by releasing it, reception only is possible. Thus the equipment at either end is always maintained when not in use, at the "receiving" or "stand-by" condition. Finally, at various depots along the railroad system, small transmitters are being installed for the purpose of issuing instructions to train-crews. Such a system of signalling between depots and trains is a material safeguard in foggy and rough weather, and it is a system which is now being adapted for passenger train communication.